Magnetic circularly polarized luminescence spectra of Eu(.beta.-diketonate)3X2 complexes in nonaqueous solution

Abstract

Unpolarized emission spectra and magnetic field induced circularly polarized emission spectra are reported for EuC13 and for five different tris(|8-diketonate) Eu(III) complexes in methanol and in yV./V-dimethylformamide solutions. Analysis of the EuCl3 spectra suggests the predominance of axially symmetric coordination species with C3v point-group symmetry.Analysis of the tris(/3-diketonate) Eu(III) spectra show the predominance of nonaxially symmetric structures with very strong orthorhombic crystal field components. The observed 7F2 *-5D0 and 7F, *-5D0 emission intensity ratios exhibit a strong sensitivity to the structural details and chemical nature of the ligand environment, with the magnitude of /(7F2 «-5D0):/(7F! *-5D0) correlating closely with ligand or ligand substituent polarizabilities. The latter is explained in terms of the ligand dipolar polarization model for 4f -4f electric dipole intensities. The 7F0 *-5D0 transition intensity (relative to that of 7F, •*-5D0) is also observed to be very sensitive to the ligand environment, and this is attributed to its "stealing" intensity from the 7F2 «-5D0 transition via a mechanism involving crystal field induced mixings between the 7F0 and 7F2 (and 5D0 and 5D2) multiplet states. to F.S.R.) and the National Institutes of Health (Grant R01-CA-30148 to L.M.V.).

Interpretation of europium(III) spectra

“…This technique has been used mainly to investigate europium(III) coordination compounds in solution [608][609][610][611][612][613][614]. Table 8 for an example [81]).…”

Some misconceptions concerning the electronic spectra of tri-positive europium and cerium

“…As discussed above, the 5 D 0 -7 F 2 transition is a forced electric dipole transition and according to the ligand dipole polarization model, its intensity is proportional to the square of the ligand dipolar polarizability. 26 The comparison of the ratio R, i.e., I( 5 D 0 -7 F 2 )/I( 5 D 0 -7 F 1 ), which has been employed in great detail in many publications with misleading conclusions, is considered under three regimes.…”

Rare-earth beta-diketonates

“…The absence of splitting of the 5 D 0 → 7 F 0 transition indicated that only one monomeric species exist in solution. Later on Richardson and coworkers (Foster et al, 1983) extended these studies to the complexes [Eu(hfac) 3 ], [Eu(tfac) 3 ], [Eu(bpp) 3 ], [Eu(ftac) 3 ] and [Eu(ftac) 3 (phen)]. MCPL spectra were measured in DMF and in methanol.…”